The general figure that most nutritionists agree on is that protein (aminos) last in the bloodstream approximately three to four hours. That’s part of the reason for the common recommendation for a meal frequency of six small meals per day. Almost all serious bodybuilders and fitness enthusiasts eat a meal every 2 ½ to 4 waking hours. However, you’re correct that different proteins and combinations of protein with other foods can change the speed of digestion and absorption.

In 1997 a lot of interest was stirred up on the subject of “fast” versus “slow” proteins after a study was published by French researcher Yves Boire (Fast and slow dietary proteins differently modulate postprandial protein accretion, Proc Natl Acad Sci. 94, 14930-14935, 1997). There are two types of protein in milk: Whey and Casein. This study, which is commonly quoted in protein advertisements, showed that whey is a soluble fast acting protein. In this respect, whey is often referred to as an 'anabolic’ protein due to it’s impact on increasing protein synthesis. This makes whey ideal for post workout nutrition and is the reason why whey is almost always the protein used in post workout drinks, in combination with fast acting (high glycemic) carbohydrates such as maltodextrin + dextrose.

The study also showed that casein is a slower protein because it clots in the stomach, which delays gastric emptying time and causes a slower release of amino acids into the bloodstream. In this respect, casein is often referred to as an “anti-catabolic’ protein due to it’s impact on decreasing protein breakdown. Because you tend to go into a catabolic state about half way through the night while you are sleeping, this is the reason you hear the recommendation for casein as a nighttime protein (taken right before bed).

In the 1997 Boire study, plasma amino acids remained elevated for up to 7 hours after ingestion of the casein protein. The authors said,

"These two dietary proteins have different metabolic fates and uses. After whey protein ingestion, the plasma appearance of dietary amino acids is fast, high and transient. This amino acid pattern is associated with an increased protein synthesis and oxidation and no change in protein breakdown. By contrast, the plasma appearance of dietary amino acids after a casein protein meal is slower, lower and prolonged with a different whole body metabolic response: Protein synthesis slightly increases, oxidation is moderately stimulated, but protein breakdown is markedly inhibited."

These are very interesting findings. However, I believe that far too many erroneous conclusions have been drawn from this study and similar studies and that this information has even been manipulated to sell “night time” and “anti catabolic” supplements.” These products are often pushed with fear-based tactics such as, “If you don’t use our nighttime protein formula before bed, you’re going to lose all your hard earned muscle while you’re sleeping and all your hard work in the gym will be for nothing.”

Before coming to such conclusions, all the factors must be carefully weighed. For example, I looked up the full text of this study, read the whole thing and discovered that the study was conducted on subjects that had been fasted for 10 hours! That is the exact opposite of the situation that would occur at night in a typical bodybuilder’s diet: They would have been consuming frequent meals with protein every 3 hours up to that last night time meal, which is as far from fasting as you can get.

Furthermore, the study did not account for the fact that when protein is eaten in combination with other foods, this can slow the gastric emptying rate. Foods that contain fat and fiber slow the time it takes to digest a meal. Whey protein taken by itself is not the same thing as whey protein with a tablespoon of flax oil, or whey protein with oatmeal, ground flaxseeds and an apple (favorite of mine).

There is just enough truth in the "slow versus fast protein" issue that it has been used as ammunition in the advertising for all kinds of new “nighttime” and “anti-catabolic” protein products. Supplement companies release these new products regularly to remain competitive and to keep their sales curve heading upwards. But is it worth spending your money?

Nutrition expert John Berardi, PhD, put it this way: "Why the need for fancy overnight protein products? At a price of four to seven bucks per 50g of protein (based on the brands I've looked at), I can't see one. Considering that plain old cottage cheese can accomplish this goal, these formulations aren't so revolutionary."

Although having a slow-release protein shake before bed is not a bad idea, you could just as easily eat cottage cheese and get the same effect (if you’re not lactose intolerant). Eating fat with protein meals also delays gastric emptying time and can produce a similar effect. The “old timers” used to eat steak and eggs at night for the same reason. Some bodybuilders have even reported that they maintained their lean body mass while dieting on fat and protein, even though they only ate three meals per day.

The type of protein you eat and what you eat it with can definitely have an impact on digestion and absorption rate and subsequently, how long you stay in positive nitrogen balance. This can and should be implemented into a nutrition program that takes nutrient timing into account - most importantly after your workout (fast acting proteins and high GI carbs) and also before bedtime. However, you could just as easily use real food.

Although whey and casein are both great proteins and have some interesting properties, I believe that the primary benefit of protein supplements and meal replacements is convenience. It’s a lot of work and takes a lot of dedication to prepare and eat six whole food meals per day. Meal replacements and protein powders make it a lot easier to get your meal with a serving of protein every three hours. Incidentally, most meal replacement formulas these days are not 100% whey, they are a mix of whey, casein, and often other protein species as well. Based on the research, protein mixes make a lot of sense.

Bottom line: Unless I see some well designed and independent studies that directly compare protein powders to protein foods and prove the superiority and cost effectiveness of powders over food, then I don’t believe it makes that much of a difference either way. If you think about it, protein powder is really just "powdered food" anyway. With the possible exception of a liquid post workout drink - especially on weight gain programs - I'm partial to whole foods over powders, given the choice.

Whether you choose to use whole food or supplements is up to you and will probably be dictated more by your need for convenience than anything else (and possibly, your budget). If you’re eating high quality, complete proteins every three hours and if you’re handling post workout nutrition properly, then beyond that, I think it's trivial to worry about the "speed" of each individual type of protein and whether its in powder or food form.
 

Tom Venuto is a lifetime natural bodybuilder, personal trainer, gym owner, freelance writer and author of BURN THE FAT, FEED THE MUSCLE: Fat Burning Secrets of the World's Best Bodybuilders and Fitness Models. Tom has written over 140 articles and has been featured in IRONMAN magazine, Natural Bodybuilding, Muscular Development, Muscle-Zine, Exercise for Men and Men's Exercise. Tom is the Fat Loss Expert for Global-Fitness.com and the nutrition editor for Femalemuscle.com and his articles are featured regularly on literally dozens of other websites.

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